CS242853B2 - Method of methyl-tertiary butyl ether preparation - Google Patents

Abstract

1506461 Removing isobutene from hydrocarbon streams SNAMPROGETTI SpA 13 May 1975 [21 May 1974] 20210/75 Heading C5E [Also in Division C2] A process for selectively removing isobutene from a hydrocarbon stream comprises feeding a primary alcohol and a C 4 hydrocarbon stream comprising isobutene and buta-1,3-dene, where there is at least 4% by weight of buta-1,3-diene in the hydrocarbon stream, to a synthesis zone containing as catalyst an acid ion exchange resin, at a temperature in the range from 60‹ to 120‹ C., with a liquid hourly space velocity (expressed as the volume of liquid per hour and per volume of catalyst) in the range of from 5 to 35, and where the temperature in the synthesis zone is approximately in accordance with the following equation where T is the temperature expressed as ‹ C. and LHSV is the liquid hourly space velocity; and separating downstream of the synthesis zone the resulting alkyl tertiary butyl ether from other compound(s) present, by distillation. Reference has been directed by the Comptroller to Specification 1,176,620.

Description

In particular, the present invention provides a process for preparing methyl tert-butyl ether starting from methanol and isobutylene in the presence of butadiene.

In the continuation of the description, reference will only be made to said preparation of methyl tert-butyl ether, although the process is strictly suitable for the synthesis of each alkyl tert-butyl ether starting from any primary alcohol.

It is known that methanol can be added to isobutylene to form methyl tert-butyl ether (EMTB).

The reaction is catalysed by inorganic acids (e.g. sulfuric acid), organic acids (sulfo acids) and ion exchange resins: sulfonated styrene-divinylbenzene copolymers are particularly suitable for this purpose.

The methanol addition reaction is selective for isobutylene and other olefins having a tertiary double-bonded carbon atom, while under the same operating conditions linear olefins such as butene-1 and butene-2 (cis and trans) are inert: the selectivity mentioned in the previous lines allows used to synthesize the EMTB of isobutylene contained in the commercial fractions, for example, the C 1 -olefin fraction obtained in the catalytic cracking.

It is known that the same styrene-divinylbenzene resins used as catalysts in EMTB synthesis also catalyze the dimerization and polymerization of dienes: this causes the use of olefinic butadiene-rich fractions, e.g. EMTB, diene must first be extracted or selectively hydrogenated (British Patent No. 957,000). Confirmation of the necessity mentioned earlier can be found in the earlier patent literature, in which in all the cases recorded butadiene is absent or not more than 2 to 4% (see Italian Patent No. 877 818, French Patent No. 1 256,388 and Offenlegungsschrift of Germany (No. 2,011,826).

Obviously, all of these limitations apply to the use of steam cracking fractions and that even the proposed solutions, prior extraction of butadiene or its prehydrogenation do not result in a very practical solution, since the first eventuality requires EMTB synthesis to be downstream of the butadiene extraction unit. then results in the loss of valuable hydrocarbon.

It has been found that, under suitable operating conditions, isobutylene etherification can also be carried out in the presence of a considerable amount of butadiene, its losses being limited to values less than 2%. Losses are essentially due to the formation of butenyl ethers, dimers and codimers.

The present invention provides a process for the preparation of methyl tert-butyl ether by reacting methanol with a C ₄ - hydrocarbon fraction obtained by steam cracking in the presence of an ion exchange resin with a skeleton of a styrene-divinylbenzene copolymer optionally containing sulfone groups at 60 to 120 ° C. whose principle is that the reaction is carried out under conditions where the dependence of the spatial velocity of the LHSV

LHSV = 1/2 t - 25, where t stands for temperature in degrees Celsius.

The method according to the invention can also be used к separation of isobutylene from _{C4-hydrocarbon} fraction comprising butadiene etherification of isobutene and primary alcohol, followed by separation of the resulting ether by distillation.

The possibility of synthesizing EMTB from butadiene-rich fractions solves the above-mentioned problems and, moreover, offers the opportunity to obtain as a by-product an olefinic fraction enriched with even more butadiene, resulting in the advantage of such diene being optionally isolated.

The selective etherification of isobutylene in favor of a considerable amount of butadiene is possible because operating conditions have been found which allow for kinetic control of the butadiene secondary reactions; under conditions other than those found, losses on butadiene may also reach 20% to 30%.

Some examples are now given in order to better illustrate the invention, but not j ^e j in any way ommeoovt.

Example 1

130 g of C ₄ -olefinized steam cracking fractions of propylene composition by weight propane isobutane n-butane% butene 1 isobutylene butene 2 trans butene 2 cis

1,3 butadiene

6,03 missing

0.86

3.73

16.44

29.19

5.89

4.29

39.57 were put into an autoclave together with 20 g of mmeanolu, mooární ratio of isobutylene / oetanol · = l, ^03, and 12 ^g Arn ^ elyst ¹⁵ used ^for the I ^ ^^ or tal. Mixture of intensive stirring.

During this time, they take samples that reacted ^p s analysis gave C for these results.

Time (minutes)

30 60

120

150

Isoeuty-

len (% hmc> o.) 66.53 75.01 79.82 75.10 Me- tanol (% wtc> o.) 68.47 77.62 87.69 92.26 Conversion of butaHenu smaller smaller (% hmoo) than 0.1 than 0.1 1,2 4.66 Conversion of oil smaller smaller smaller smaller butenes (% hmoo.) than 0.1 than 0.1 than 0.1 than 0.1

71.54

93.25

8.76 less than 0.1

Losses on butadiene were caused by the increased methyl-buffers of the ethers and less minor dimers (vinylcycohexene) and codimers. As can be seen from Example 1 by the continuous process, the longer duration not only reduces buta-henna recovery but also negatively affects the conversion of isobutylene; under the conditions of the dropper, an iso-ethylene conversion was achieved after 60 minutes and then changed.

This behavior results from the fact that EMTB, mmeanoi and islethyllet achieve thermodynamic equilibrium in a short time, and then when the meeanoi is consumed to produce butadiene ethers, the system reacts again by decomposing the EMTB to its constituents, thereby equilibrating set up again.

Příkaady 2, 3 and 4

The same olefin fraction as in the slurry 1 was reacted continuously with methane in the

Amberlyst 15 in a flow-through reactor, versions are given in the table below. Working conditions and obtained con Examples 2 3 4 Temperature (° C) 60 80 80 LHSV 5 5 15 Dec Molar ratio of isobu- Tylene / methanol 1 1 1 Isobutylene conversion 77.6 70.7 79.1 Conversion of butadiene 1.3 11.5 1,8 Linear conversion smaller than smaller than smaller than butenes 0.1 0.1 0.1

Considerations similar to those given in Example 1 result from the tests of Examples 2, 3, 4 conducted continuously in a closed reactor (continuous closed flow reactor). It has therefore been found that once the temperature is selected, the optimum space velocity of the LHSV exists, higher temperatures result in higher butadiene recovery but lower isobutylene conversions than equilibrium, LHSV lower than optimal results in secondary butadiene reactions and lower isobutylene conversions.

Claims (1)

SUBJECT OF THE INVENTION A process for preparing methyl tert-butyl ether by reacting methanol with a C ^-hydrocarbon fraction obtained by steam cracking in the presence of an ion exchange resin with a skeleton of a styrene-divinylbenzene copolymer, optionally containing sulfone groups, at a temperature of 60 to 120 ° C, The reaction is carried out under conditions where the relationship between the space velocity of the LHSV and the reaction temperature applies LHSV = 1/2 t - 25, where t stands for temperature in degrees Celsius.